Diamond abrasive tool



Patented Mar. 24, 1942 DIAMOND ABRASIVE TOOL Edgar W. Engle, GrossePointe Park, Mich., as-

signor to Carboloy Company, 1110., Detroit, Mich., a corporation of NewYork No Drawing. Application May 31, 1939, Serial No. 276,585

2 Claims.

The present invention relates to diamond impregnated hard metalcompositions and more particularly to an abrasive composition whichconsists of diamond particlesembedded in a hard metal composition matrixwhich contains metal from the group copper and silver.

Prior to the presentinvention abrasive compositions have been made whichconsist of dia mond particles embedded in a hard metal compositionmatrix consisting for example of tungsten carbide and cobalt. Acomposition of this character is disclosed in Taylor Patent 1,996,598.

Diamond particles employed in any grinding wheel or drill constitute alarge portion of the cost of such articles and it is highly desirablethat the diamonds be .held firmly in position. While the cementedcarbide matrix disclosed in the Taylor patent holds the diamonds firmlyin position in drills, wheel dressers and the like, I have found that inabrasive wheels, cutting-off wheels, laps, and the like, it is possibleto obtain even greater gripping action on the diamond particles if thecemented carbide matrix for the diamonds contains a relatively smallquantity of metal from the group copper and silver.

In carrying out my invention, I employ as the matrix for the diamondparticles a mixture of tungsten carbide and metal of the iron groupsuchas cobalt to which a few per cent of copper, or silver, or both hasbeen added. The cobalt content of the matrix may constitute from about 3to about 25% by weight of the mixture of tungsten carbide and cobalt,the quantity of cobalt employed depending upon the work to be performed.A tool consisting of about 75 %'of a mixture of WC and 16% Co, /2% ofmetal from the group copper and silver and 19% diamond particles givesvery satisfactory results.

The quantity of diamond particles employed in an abrasive tool may varybut in general the quantity employed will be the maximum quantity whichthe matrix will hold together securely. In cut-oif wheelswhere-considerable toughness is contain less cobalt, since'there will bea greater thickness of matrix surrounding each diamond particle. With agiven amount of wheel wear there will be more binder to be removed withwheels containing a lesser percentage by volume of diamond with theresult that if the binder is too tough the tendencyto glaze overtheexposed diamond particles will be increased. In pro ducing a thindisc cutting wheel with a volume relation of two parts matrix and onepart diamond, I use an inherently tougher matrix than in the case of asurface grinding wheel with approximately equal volumes of diamond andrequired the volume of diamond particles may ployed, it maybe found thatwith diamonds within mesh limits of 20 to 120, there is not enoughmatrix material to grip all the diamonds.

As the percentage volume of diamonds decreases the matrix can be lesstough, that is,

matrix. Another factor which determines the composition of the matrix isthe peripheral speed at which the wheel operates. The matrix must havesufiicient strength and toughness so that the wheel will not fracturefrom the forces developed in rotation.

The quantity of copper or silver or both employed in the cementedcarbide matrix may vary but if too much is employed the copper or silverwill glaze the wheel and prevent cutting action. A matrix consisting ofabout 92% or 93% of a mixture of tungsten carbide and 16% cobalt withabout 7% copper or 8% silver gives very satisfactory results. Thediamond particles which I employ are capable of passing through a 20 to120 mesh or 'even finer screen but preferably are capable of passingthrough a 40 to mesh Grams of test Wheel wear block in change ofdiameter moved r .001 re uction in wheel diameter Weight in grams ofcemented carbide removed from test block Inches Similar wheelscontaining the same quantity and size of diamond particles embedded in acemented carbide matrix consisting of 91.9% of a mixture of WC and 16%Co. with 8.1% silver gave the following results:

Grams of tcst block "re-' moved r .001" re uction in whccl diameter\\'heel wear in change in diameter Weight in grams of cemented carbideremoved from test block Inclm 5.003 s. we

Similar wheels containing the same quantity and size of diamondparticles embedded in a cemented carbide matrix consisting of 93% of amixture of tungsten carbide and 16% cobalt with 7% copper gave thefollowing results:

Grams of test block removed r .001" re uction in wheel diameter Wheelwear in change of diameter Wcight in grams of cemented carbide removedfrom test block Inches 6.200 .(Xi2 3.145

In the manufacture of the above abrasive tools the tungsten carbide andcobalt is thoroughly mixed for example in a ball mill. The mixedmaterial is then spread out in a thin layer and powdered copper orsilver or both added and mixed therewith, usually by hand. Thereafterthe diamond-particles are added. These also are hand mixed with thepowdered matrix material. When mixed to the desired extent the materialis placed in a mold care being taken that the diamond particles remainevenly distributed throughodt the powdered metal matrix. A pressure'oi'about 2500 to 3000 lbs. per square inch is applied to the powderedmaterial in the mold while it has a temperature of about 1400 to 1700"C. The pressed material may be heated in any suitable atmosphere, forexample in hydrogen.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An abrading tool'having a portion thereof consisting of diamondparticles distributed in a matrix which consistsof a cemented carbidecontaining an appreciable quantity and up to about 8% silver.

2. An abrading tool having a portion thereof consisting of diamondparticles distributed in a matrix which consists of a cemented carbidecontaining about 8% silver, said cemented carbide consisting of about16% cobalt with the remainder tungsten carbide.

EDGAR W. ENGLE.

